1. Field of the Invention
The present invention relates to an image processing apparatus and an image processing method, and more particularly, to an image processing apparatus and an image processing method used for ophthalmic care and the like.
2. Description of the Related Art
An examination of fundus of the eye is widely performed for the purpose of a diagnosis in early stage of a disease that usually ranks high in adult disease or cause of blindness. A scanning laser ophthalmoscope (SLO) which uses a principle of a confocal laser microscope is an apparatus that performs a raster scanning on a fundus of the eye with laser light which is measurement light and obtains a two-dimensional image of the fundus of the eye from return light with a high resolution at a high speed.
In recent years, an adaptive optics SLO has been developed which includes an adaptive optical system for measuring an aberration of an eye to be inspected in real time with a wavefront sensor and correcting the aberrations of measurement light and return light generated at the eye to be inspected with a wavefront correction device, enabling an acquisition of a two-dimensional image with a high lateral resolution. In addition, by extracting photoreceptor cells in a retina by using a required two-dimensional image of a retina, it is attempted to diagnose a disease and to evaluate a response to a drug from an analysis of a density and a distribution of the photoreceptor cells.
As an example of performing a visualization of the photoreceptor cells by using the adaptive optics SLO, there has been proposed, in Kaccie Y. Li and Austin Roorda, “Automated identification of cone photoreceptors in adaptive optics retinal images,” J. Opt. Soc. Am. A, May 2007, Vol. 24, No. 5, p. 1358, an ophthalmoscopy apparatus capable of acquiring a two-dimensional image of a retina and performing an automatic extraction of the photoreceptor cells. In this ophthalmoscopy apparatus, a two-dimensional image of a retina with a high lateral resolution is acquired, and by removing a high frequency component by using periodicity of arrangement of the photoreceptor cells extracted from the image, an automatic detection of the photoreceptor cells is performed based on a maximum value detection. In addition, by using a detection result of the photoreceptor cells, a density of the photoreceptor cells and a distance between the photoreceptor cells are measured, and an analysis based on a Voronoi analysis of a spatial distribution. Further in Jacque L. Duncan, et al., “High-Resolution Imaging with Adaptive Optics in Patients with Inherited Retinal Degeneration,” Investigative Ophthalmology & Visual Science, July 2007, Vol. 48, No. 7, p. 3283, an analysis is performed on a correlation between a density of detected photoreceptor cells and a retinal disease, and an association of an area in which the density of the photoreceptor cells is decreased with an area in which a visual sensitivity is decreased or cystoid macular edema (CME) is performed.
In the above described example, the analysis of the photoreceptor cells is performed with a method of, for example, calculating the density of the photoreceptor cells and the distance between the photoreceptor cells with a two-dimensional image acquired by the adaptive optics SLO. An abnormality such as a low density area found from the analysis is then compared with information obtained from another modality, for example, a change of a retinal thickness observed by an OCT, and a debate is held whether or not the abnormality matches the observed site.